#include<iostream>
#include<cmath>
#include<iomanip>
using namespace std;
double S(double x1, double y1, double x2, double y2)
{
	return sqrt(((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2)));
}
int main()
{
	double x1, y1;
	double x2, y2;
	double x3, y3;
	cin >> x1 >> y1;
	cin >> x2 >> y2;
	cin >> x3 >> y3;
	double a = S(x1, y1, x2, y2);
	double b = S(x1, y1, x3, y3);
	double c = S(x2, y2, x3, y3);
	double p = (a + b + c) / 2;
	cout <<fixed<<setprecision(2)<< sqrt(p * (p - a) * (p - b) * (p - c));
	return 0;
}